By Chris Cardinal on December 8th, 2009

Google today announced Speed Tracer as part of their Google Web Toolkit offerings. While most of the GWT focuses on enabling developers to create web applications in Java (which compiles down to optimized JavaScript), Speed Tracer is a useful profiling tool for any developer wrestling with XMLHttpRequest.

What makes Speed Tracer different?

Developers have long used Firebug to identify what AJAX requests were causing bottlenecks and to analyze responses to those requests. Firebug is an extremely powerful tool and does a serviceable job with this approach, but Speed Tracer takes things one step further, analyzing the “sluggishness” of your application by examining how busy or blocked the UI is in your browser. This can help developers analyze why their application feels slow, instead of simply focusing on network-based bottlenecks.

Speed Tracer makes use of specific, unique APIs built into Webkit for this very purpose, which gives it a unique advantage compared to other profiling tools. Instead of simply guessing and checking, developers will now have full visibility into what’s causing their applications to appear slow:

Using Speed Tracer you are able to get a better picture of where time is being spent in your application. This includes problems caused by JavaScript parsing and execution, layout, CSS style recalculation and selector matching, DOM event handling, network resource loading, timer fires, XMLHttpRequest callbacks, painting, and more.

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